The RMT union's complaints relate to the transfer of Piccadilly Line control-room services to a new centre in Hammersmith.
Transport for London plans to replace a number of separate control centres with a single one from 2017.
The Rail, Maritime and Transport Union says the move will cause job losses - and that there are also issues with rates of pay and the lack of "any meaningful offer for Service Control staff for the Olympic period."
More top news
At least 2,000 people took to the streets of Baltimore yesterday to demand answers over the death in custody of Freddie Gray
Planning on going to the London Marathon tomorrow? Read our handy guide first!
Celebrations to mark St George's Day have started in Trafalgar Square with feasts and tea to be found in abundance.